The oxazolidinone antibacterial agents are a novel synthetic class of antimicrobials with potent activity against a number of human and veterinary pathogens, including gram-positive aerobic bacteria such as multiply-resistant staphylococci and streptococci, anaerobic organisms such as bacteroides and clostridia species, and acid-fast organisms such as Mycobacterium tuberculosis and Mycobacterium avium. In particular, the oxazolidinone compounds of structures I-V have been found especially effective. ##STR1##
However, certain oxazolidinones generally have poor activity at a useful level against aerobic gram-negative organisms such as E. coli, Haemophilus influenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, or Klebsiella pneumoniae. Thus, the use of these oxazolidinone antibacterial agents alone is limited to infectious states due to gram-positive bacteria. Accordingly, it is among the objects of the present invention to provide a process for enhancing the inhibitory spectrum of the oxazolidinones. We have now discovered that when the oxazolidinone antibacterial agents are administered with an arginine derivative, a pronounced synergic effect against gram-negative organisms is produced. The effective amount of an oxazolidinone antibacterial agent to be fully efficacious against aerobic gram-negative organisms is much lower than would be needed if an oxazolidinone was administered without these arginine derivatives.